A capacitor is a standard component in many electronic circuits. A capacitor typically consists of first and second conductive electrodes separated by a dielectric insulating layer disposed between the first and second conductive electrodes. The conductive electrodes in a capacitor can be made of metals or semiconductors that are heavily doped with impurities, while the dielectric layer can be an oxide or other insulating materials (e.g., nitrides and ceramics). Compared to off-chip capacitors, on-chip MIM (metal-insulator-metal) capacitors typically have smaller capacitance values on the order of microfarads per square micrometer (μF μm−2) due to their restricted size.
In order to achieve effectively large capacitance values, a MIM capacitor can be fabricated in a deep trench in the front end of line (FEOL) in a semiconductor substrate where active devices are fabricated, which offers a large capacitance value compared to a standard planar capacitor. However, such deep trench MIM technology on the FEOL requires additional area on the semiconductor substrate and provides poor signal interference. Therefore, it is desirable to provide a method for forming a MIM capacitor with a large capacitance and a small chip area requirement.